The present invention relates generally to a shift assist control arrangement for an engine, and more particularly to an improved shift assist control arrangement for a split-bank, multicylinder engine.
In many forms of marine propulsion systems, the powering internal combustion engine drives a propulsion device through a transmission. Conventionally, the transmissions utilized for this purpose are bevel gear forward, neutral, reverse transmissions shifted by means of dog clutches. These transmissions have the advantage of being able to transmit large amounts of power while maintaining a relatively small and compact assembly. However, this type of transmission has problems in that the engagement of the dog clutches can be difficult at times. This is particularly true if the engine is running at a high speed or developing a large amount of power at the time the shift is attempted.
It has, therefore, been the practice to provide a variety of shift assisting mechanisms which will automatically reduce the speed of the engine when high shifting forces are encountered. For example, Japanese Patent No. 2759475 and U.S. Pat. No. 6,098,591 disclose shift assist arrangements.
This invention relates to an improved engine control system and method and more particularly to an improved control system and method for engines and particularly to drive transmissions incorporating shift assists. The preferred embodiments of the invention provide an improved shift assist system for a watercraft and particularly for watercraft with an outboard motor.
In accordance with one aspect of a preferred embodiment of the shift assist control system of this invention, the shift force detecting unit includes a shift force detection switch and a neutral switch connected to a shift mechanism. The shift mechanism is connected to a dog clutch in the transmission unit. The force detecting unit relays information to the electronic control unit, and engine torque is then lowered depending on the value of the current traveling through the force detecting unit. A significant feature of the preferred embodiments of this invention is that the shift assist system is not adversely affected by abnormal control circuit faults including a short circuit or an open circuit failure of the shift control system.
In accordance with another aspect of a preferred embodiment of the invention, operation of the operator controlled shifting is detected to effect a change in transmission ratio and reduce the torque of the engine in response to a sensed operation of the operator controlled shifting.
A further aspect of a preferred embodiment of the invention is a shift assist control system including an electronic control unit that responds to both normal shifting of the engine and abnormal conditions produced by either an electrical disconnect with the shift force-detecting switch or a short circuit in the force-detecting switch.
Another aspect of a preferred embodiment of the invention is a shift assist system which normally supplies a current of known value to the engine""s electronic control unit. However, during a shift that requires an excessive force or an abnormal condition of circuit disconnect or short-circuit, this current value is changed and this change in current value is detected by the electronic control unit to automatically reduce the speed of the engine.